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Planning for biodiversity and cereal production in the Gariep Basin : a conservation perspective

Ginsburg, Aimee (2006-04)

Thesis (MSc)--University of Stellenbosch, 2006.

Thesis

ENGLISH ABSTRACT: Biodiversity feature richness and cereal production potential increase west to east
across South Africa's Gariep basin, the regional focus area in the Southern African
Millennium Ecosystem Assessment. lrreplaceability, developed for measuring biodiversity
value, provides a unit free, spatially explicit measure that can be used to measure an area's
importance in terms of cereal production. It provides a common currency to measure
competing land-uses. This study models cereal production potential for four cereal types
(maize, millet, sorghum, wheat) and sets three cereal production targets, based on minimum
nutritional cereal demands and models of actual consumption rates.
Chapter 2 uses C-Plan to determine irreplaceability and compares the irreplaceability
values for cereal production potential and biodiversity. Higher cereal production targets
increase the irreplaceability of sites for cereal production and increase the number of sites
with high irreplaceability for both biodiversity and cereal production. These sites thus have
high potential for conflict between these land-uses. Areas of conflict occur primarily across
the central eastern region, largely in the grassland biome. The biodiversity features and cereal
production potential of these sites are known, thus making potential trade-offs involved in the
conservation of these sites explicit.
Sites with conflict potential can be avoided using area selection algorithms that
maximise conservation target achievement while minimising the cost to cereal production. CPlan'
s simple iterative heuristic approach to minimising costs succeeds in avoiding some
areas of conflict potential but more complex algorithms provide better solutions. The
simulated annealing algorithm available in another conservation planning software platform,
MARXAN, offers a more complex consideration of penalties and costs associated with
meeting conservation targets and minimising cereal production costs. Chapter 3 finds that the
balance between the penalties for not achieving all biodiversity targets and those for
exceeding the cereal cost thresholds in MARXAN are critical, impacting the achievement of
certain biodiversity feature targets. Important penalties include the conservation feature
penalty factor, the cost threshold, and the cost threshold control parameter. MARX.AN
generates numerous solutions for a single problem, providing a measure of a site's selection frequency over a number of runs. The central eastern region has highest variability in
selection frequency where both cereal production and biodiversity irreplaceability are high.
As cereal production targets increase, sites in this region become more difficult to avoid and
trade-offs are unavoidable.
Comparing the software, chapter 4 concludes that the relationships between the inputs
and planning parameters on outputs are crucial for effective conservation decision making. CPlan'
s sensitivities are restricted to the combination size and site selection rules. MAR.XAN
requires numerous input parameters that collectively provide more variable outputs. Further
documentation on best and current practices in MARXAN, sensitivities of conservation
outputs to input parameters, and awareness of these sensitivity in capacity building exercises
are required to guide decision makers. Irreplaceability allows the comparison of two different
objectives and the potential trade-offs that might exist. Explicit inclusion of cereal production
potential into systematic conservation planning frameworks generates more cost effective and
socially acceptable reserve solutions that strengthen the partnership between conservation and
civil society.
Key Words: conservation planning, biodiversity, cereal production, irreplaceability, tradeojfs,
opportunity costs, MARXAN, C-Plan.